Technical Field
The present disclosure relates to a semiconductor device.
Related Art
In a semiconductor device configuring a power semiconductor device, such as a power metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT), a protecting film configured by an insulator such as polyimide is provided on the outermost face of the semiconductor device.
As technology related to patterning of polyimide films that function as protecting films, for example, Japanese Patent Application Laid-Open (JP-A) No. H09-129589 discloses a polyimide film patterning method including: forming a polyimide film on a substrate, forming a resist film on the polyimide film; forming a resist pattern by developing the resist film using a developer fluid after exposing the resist film; and etching the polyimide film by using the developer fluid for the resist film, with the resist pattern serving as a mask.
Further, JP-A No. H09-17777 discloses a semiconductor device manufacturing method that includes, after patterning by developing and etching a polyimide precursor resin and a positive resist, curing the polyimide precursor resin by heat treatment in a state in which the positive resist remains, and then, removing the etching residue of the positive resist and the polyimide by dry etching using the positive resist serving as a mask.
A power semiconductor device such as a power MOSFET or IGBT is configured including: plural gates extending in straight lines disposed parallel to each other on a front face of a semiconductor substrate; a conductive film that covers the front face of the semiconductor substrate so as to bury the plural gates; and a protecting film configured by an insulator such as polyimide that includes an opening where the conductive film is partially exposed. In such a semiconductor device, undulations occur on the semiconductor substrate due to providing plural gates extending in straight lines disposed in parallel to each other on the front face of the semiconductor substrate, and plural concave portions (grooves) extending in straight lines along the extension direction of the plural gates are formed on the front face of the conductive film as a result of the undulations. The protecting film is formed by applying a resin such as polyimide to the front face of the conductive film, which has plural concave portions (grooves), and then, the opening is formed in the protecting film using photolithography. A resist mask having a pattern corresponding to the opening is formed on the front face of the protecting film, and the opening is formed by etching the protecting film through the resist mask. Note that a developer fluid for the resist mask can be employed as an etchant for the protecting film. A typical shape for the opening of the protecting film is a square or rectangle having edges parallel to the extension direction of the plural gates, namely, the extension direction of the plural concave portions formed on the front face of the conductive film.
However, in semiconductor devices having such a structure, string-like protecting film residue remains on the front face of the exposed conductive film in the opening of the protecting film at a stage at which thermal curing treatment of the protecting film has completed. In a case in which wires are bound to the front face of the conductive film exposed in the opening of the protecting film, deficient bonding of the wire may occur, if protecting film residue adheres to the front face of the conductive film. Further, in a case in which an external connection terminal is formed on the front face of the conductive film, deficient connection between the conductive film and the external connection terminal may occur if protecting film residue adheres to the front face of the conductive film.